FIG. 1 shows a standard architecture of first known systems comprising two devices (hereafter called “local device” 16L and “distant device” 16D), connected together by a wired link 8 (e.g. an Ethernet link implemented as a copper cable). Each device comprises a physical layer unit (also referred to as “PHY”, and referenced 3 or 4), a link layer unit (also referred to as “MAC”, and referenced 2 or 5) and a processing layer unit (also referred to as “CPU”, and referenced 1 or 6). In this context, we consider the following problem: the local device 16L has to wake up the distant device 16D.
In such a context, the “Wake-On-Lan” method is currently used to wake up a distant device. The local CPU 1 transmits a magic packet on the copper cable 8, through the local MAC 2 and the local PHY 3, to the distant device 16D. This magic packet is detected by the distant PHY 4, which generates an interrupt 7 to wake up the distant CPU 6. Then the distant CPU 6 configures the distant MAC 5 to establish a link between the local CPU 1 and the distant CPU 6.
With this “Wake-On-Lan” method, a lower consumption is obtained since the CPU 6 and the MAC 5 of the distant device 16D are in “Low Power mode” and off respectively. But the PHYs 3,4 of the two devices are still powered on, and the communication between the two PHYs is always active.
As shown in FIG. 2, in second known systems, the wired link 8 between the two devices 16L, 16D is replaced by two media converters, which communicate via a transmission medium 11 (optical fiber, air, etc.). More precisely, a local media converter 12L is connected to the local device 16L via a first cable 9, and a distant media converter 12D is connected to the distant device 16D via a second cable 10.
In a basic implementation of these second known systems, the two media converters 12L, 12D are always active to be able to exchange packets:                the local media converter 12L is active, since the interface towards local device 16L (managed by PHY 13a) is active, and the transmission on medium 11 (managed by PHY 13b and using a media transceiver (not shown)) is active to maintain link between the two media converters;        the distant media converter 12D is active since the interface towards distant device 16D (managed by PHY 15b) is active, and the transmission on medium 11 (managed by PHY 15a and using a media transceiver (not shown)) is active to maintain link between the two media converters.        
In other words, in this basic implementation of the second known systems, the PHYs 13a,13b,15a,15b of the two media converters 12L, 12D are always active. So the power consumption of these second known systems may be high even if the aforesaid “Wake-On-Lan” method is implemented (i.e. with a lower consumption obtained with the CPU 6 and the MAC 5 of the distant device 16D in “Low Power mode” and off respectively).
In order to further reduce the power consumption, industry has developed “EEE modes” (“Energy-Efficient Ethernet modes”) in the Ethernet PHY, so that PHY power consumption for the local device 16L and the distant device 16D is reduced when the CPU 6 and MAC 5 of the distant device 16D and the CPU 1 and MAC 2 of the local device 16L are in the “Low Power mode”. This reduction is achieved by not transmitting packets between the two devices 16L,16D in these “EEE modes”. Compared to the “Wake-On-Lan” method, the power consumption is reduced because the two PHYs 3,4 of the local and distant devices 16L, 16D are in the “Low Power mode”. Nevertheless, the two PHYs 3,4 are still powered on (a signal is always transmitted between the two PHYs 3,4 in the “EEE modes”), i.e. are not off, and therefore consumes.
Moreover, the “EEE modes” are not available for the transmission medium 11 (optical fiber, air, etc.) of the second known systems. So, for the second known systems of FIG. 2, the power consumed by the distant media converter 12D and the local media converter 12L is not reduced very much because the PHYs 13b and 15a are fully active (only PHYs 13a and 15b are in “Low Power mode” thanks to “EEE modes”).